<!DOCTYPE html>
<html lang="en" xmlns:v-on="http://www.w3.org/1999/xhtml" xmlns:v-model="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="UTF-8">
    <title>10demo</title>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>

<div id="app">
    birthday:<input type="text" v-model="birthday"><br>
    user.name:<input type="text" v-model="user.name"><br>
    user.age:<input type="text" v-model="user.age">
</div>
<script type = "text/javascript">
    var app=new Vue({
         el:"#app",
        data:{
             birthday:1616566607004,
            user:{"name":"hello","age":1}
        },
        watch:{
             birthday(newValue,oldValue){
                 console.log(newValue);
                 console.log(oldValue)
             }
        },
        user:{
             deep:true,
            handler(obj){
                console.log(obj.name+"-"+obj.age);
            }
        }

    })
</script>
</body>
</html>